diff --git a/include/openthread-types.h b/include/openthread-types.h
index 344c31503..029583d09 100644
--- a/include/openthread-types.h
+++ b/include/openthread-types.h
@@ -324,14 +324,14 @@ typedef enum otMleAttachFilter
 /**
  * Represents a Thread device role.
  */
-enum otDeviceRole
+typedef enum
 {
     kDeviceRoleDisabled,  ///< The Thread stack is disabled.
     kDeviceRoleDetached,  ///< Not currently participating in a Thread network/partition.
     kDeviceRoleChild,     ///< The Thread Child role.
     kDeviceRoleRouter,    ///< The Thread Router role.
     kDeviceRoleLeader,    ///< The Thread Leader role.
-};
+} otDeviceRole;
 
 /**
  * @}
diff --git a/include/openthread.h b/include/openthread.h
index fbb250c87..19b0b4d7b 100644
--- a/include/openthread.h
+++ b/include/openthread.h
@@ -36,6 +36,7 @@
 #define OPENTHREAD_H_
 
 #include <stdint.h>
+#include <stdbool.h>
 
 #include <openthread-types.h>
 
@@ -367,7 +368,7 @@ ThreadError otSetPanId(otPanId aPanId);
  *
  * @returns A pointer to the first Network Inteface Address.
  */
-const otNetifAddress *otGetUnicastAddresses();
+const otNetifAddress *otGetUnicastAddresses(void);
 
 /**
  * Add a Network Interface Address to the Thread interface.
@@ -651,7 +652,7 @@ void otRemoveMacWhitelist(const uint8_t *aExtAddr);
  * @sa otDisableMacWhitelist
  * @sa otEnableMacWhitelist
  */
-void otClearMacWhitelist();
+void otClearMacWhitelist(void);
 
 /**
  * Disable MAC whitelist filtering.
@@ -663,7 +664,7 @@ void otClearMacWhitelist();
  * @sa otClearMacWhitelist
  * @sa otEnableMacWhitelist
  */
-void otDisableMacWhitelist();
+void otDisableMacWhitelist(void);
 
 /**
  * Enable MAC whitelist filtering.
@@ -674,7 +675,7 @@ void otDisableMacWhitelist();
  * @sa otClearMacWhitelist
  * @sa otDisableMacWhitelist
  */
-void otEnableMacWhitelist();
+void otEnableMacWhitelist(void);
 
 /**
  * Detach from the Thread network.
@@ -682,7 +683,7 @@ void otEnableMacWhitelist();
  * @retval kThreadErrorNone    Successfully detached from the Thread network.
  * @retval kThreadErrorBusy    Thread is disabled.
  */
-ThreadError otBecomeDetached();
+ThreadError otBecomeDetached(void);
 
 /**
  * Attempt to reattach as a child.
@@ -700,14 +701,14 @@ ThreadError otBecomeChild(otMleAttachFilter aFilter);
  * @retval kThreadErrorNone    Successfully begin attempt to become a router.
  * @retval kThreadErrorBusy    Thread is disabled or already operating in a router or leader role.
  */
-ThreadError otBecomeRouter();
+ThreadError otBecomeRouter(void);
 
 /**
  * Become a leader and start a new partition.
  *
  * @retval kThreadErrorNone  Successfully became a leader and started a new partition.
  */
-ThreadError otBecomeLeader();
+ThreadError otBecomeLeader(void);
 
 /**
  * @}
@@ -738,35 +739,35 @@ ThreadError otBecomeLeader();
  * @retval ::kDeviceRoleRouter    The device is currently operating as a Thread Router.
  * @retval ::kDeviceRoleLeader    The device is currently operating as a Thread Leader.
  */
-otDeviceRole otGetDeviceRole();
+otDeviceRole otGetDeviceRole(void);
 
 /**
  * Get the Leader's Router ID.
  *
  * @returns The Leader's Router ID.
  */
-uint8_t otGetLeaderRouterId();
+uint8_t otGetLeaderRouterId(void);
 
 /**
  * Get the Leader's Weight.
  *
  * @returns The Leader's Weight.
  */
-uint8_t otGetLeaderWeight();
+uint8_t otGetLeaderWeight(void);
 
 /**
  * Get the Network Data Version.
  *
  * @returns The Network Data Version.
  */
-uint8_t otGetNetworkDataVersion();
+uint8_t otGetNetworkDataVersion(void);
 
 /**
  * Get the Partition ID.
  *
  * @returns The Partition ID.
  */
-uint32_t otGetPartitionId();
+uint32_t otGetPartitionId(void);
 
 /**
  * Get the RLOC16.
@@ -780,14 +781,14 @@ uint16_t otGetRloc16(void);
  *
  * @returns The Router ID Sequence.
  */
-uint8_t otGetRouterIdSequence();
+uint8_t otGetRouterIdSequence(void);
 
 /**
  * Get the Stable Network Data Version.
  *
  * @returns The Stable Network Data Version.
  */
-uint8_t otGetStableNetworkDataVersion();
+uint8_t otGetStableNetworkDataVersion(void);
 
 /**
  * @}
@@ -1010,7 +1011,7 @@ int otWriteMessage(otMessage aMessage, uint16_t aOffset, const void *aBuf, uint1
  *
  * @sa otFreeMessage
  */
-otMessage otNewUdpMessage();
+otMessage otNewUdpMessage(void);
 
 /**
  * Open a UDP/IPv6 socket.
diff --git a/src/core/openthread.cpp b/src/core/openthread.cpp
index 1c9b464f0..ac816319e 100644
--- a/src/core/openthread.cpp
+++ b/src/core/openthread.cpp
@@ -62,7 +62,7 @@ static otDEFINE_ALIGNED_VAR(sThreadNetifRaw, sizeof(ThreadNetif), uint64_t);
 
 static void HandleActiveScanResult(void *aContext, Mac::Frame *aFrame);
 
-void otInit()
+void otInit(void)
 {
     otLogInfoApi("Init\n");
     Message::Init();
@@ -341,22 +341,22 @@ void otRemoveMacWhitelist(const uint8_t *aExtAddr)
     sThreadNetif->GetMac().GetWhitelist().Remove(*reinterpret_cast<const Mac::ExtAddress *>(aExtAddr));
 }
 
-void otClearMacWhitelist()
+void otClearMacWhitelist(void)
 {
     sThreadNetif->GetMac().GetWhitelist().Clear();
 }
 
-void otDisableMacWhitelist()
+void otDisableMacWhitelist(void)
 {
     sThreadNetif->GetMac().GetWhitelist().Disable();
 }
 
-void otEnableMacWhitelist()
+void otEnableMacWhitelist(void)
 {
     sThreadNetif->GetMac().GetWhitelist().Enable();
 }
 
-ThreadError otBecomeDetached()
+ThreadError otBecomeDetached(void)
 {
     return sThreadNetif->GetMle().BecomeDetached();
 }
@@ -366,17 +366,17 @@ ThreadError otBecomeChild(otMleAttachFilter aFilter)
     return sThreadNetif->GetMle().BecomeChild(aFilter);
 }
 
-ThreadError otBecomeRouter()
+ThreadError otBecomeRouter(void)
 {
     return sThreadNetif->GetMle().BecomeRouter();
 }
 
-ThreadError otBecomeLeader()
+ThreadError otBecomeLeader(void)
 {
     return sThreadNetif->GetMle().BecomeLeader();
 }
 
-otDeviceRole otGetDeviceRole()
+otDeviceRole otGetDeviceRole(void)
 {
     otDeviceRole rval = kDeviceRoleDisabled;
 
@@ -406,22 +406,22 @@ otDeviceRole otGetDeviceRole()
     return rval;
 }
 
-uint8_t otGetLeaderRouterId()
+uint8_t otGetLeaderRouterId(void)
 {
     return sThreadNetif->GetMle().GetLeaderDataTlv().GetLeaderRouterId();
 }
 
-uint8_t otGetLeaderWeight()
+uint8_t otGetLeaderWeight(void)
 {
     return sThreadNetif->GetMle().GetLeaderDataTlv().GetWeighting();
 }
 
-uint8_t otGetNetworkDataVersion()
+uint8_t otGetNetworkDataVersion(void)
 {
     return sThreadNetif->GetMle().GetLeaderDataTlv().GetDataVersion();
 }
 
-uint32_t otGetPartitionId()
+uint32_t otGetPartitionId(void)
 {
     return sThreadNetif->GetMle().GetLeaderDataTlv().GetPartitionId();
 }
@@ -431,12 +431,12 @@ uint16_t otGetRloc16(void)
     return sThreadNetif->GetMle().GetRloc16();
 }
 
-uint8_t otGetRouterIdSequence()
+uint8_t otGetRouterIdSequence(void)
 {
     return sThreadNetif->GetMle().GetRouterIdSequence();
 }
 
-uint8_t otGetStableNetworkDataVersion()
+uint8_t otGetStableNetworkDataVersion(void)
 {
     return sThreadNetif->GetMle().GetLeaderDataTlv().GetStableDataVersion();
 }
@@ -451,7 +451,7 @@ ThreadError otIp6AddressFromString(const char *str, otIp6Address *address)
     return static_cast<Ip6::Address *>(address)->FromString(str);
 }
 
-const otNetifAddress *otGetUnicastAddresses()
+const otNetifAddress *otGetUnicastAddresses(void)
 {
     return sThreadNetif->GetUnicastAddresses();
 }
@@ -527,7 +527,7 @@ exit:
     return;
 }
 
-otMessage otNewUdpMessage()
+otMessage otNewUdpMessage(void)
 {
     return Ip6::Udp::NewMessage(0);
 }